A developer is designing a serverless application for a game in which users register and log in through a web browser. The application makes requests on behalf of users to a set of AWS Lambda functions that run behind an Amazon API Gateway HTTP API.
The developer needs to implement a solution to register and log in users on the application's sign-in page. The solution must minimize operational overhead and must minimize ongoing management of user identities.
Which solution will meet these requirements?

A. Create Amazon Cognito user pools for external social identity providers. Configure IAM roles for the identity pools.
B. Program the sign-in page to create users' IAM groups with the IAM roles attached to the groups.
C. Create an Amazon RDS for SQL Server DB instance to store the users and manage the permissions to the background resources in AWS.
D. Configure the sign-in page to register and store the users and their passwords in an Amazon DynamoDB table with an attached IAM policy.